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ARS Home » Pacific West Area » Kimberly, Idaho » Northwest Irrigation and Soils Research » Research » Publications at this Location » Publication #421686
Research Project: Decipher Molecular Mechanisms for Genetic Variations in Agronomically Important Traits to Improve Sugar Beet Disease Resistance and Yield

Location: Northwest Irrigation and Soils Research

Title: Incidence, distribution, and pathogenicity of fungi growing on sugar beet roots on top of outdoor piles in Idaho

Author
item Strausbaugh, Carl

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2025
Publication Date: 1/14/2025
Citation: Strausbaugh, C.A. 2025. Incidence, distribution, and pathogenicity of fungi growing on sugar beet roots on top of outdoor piles in Idaho. Plant Disease. https://doi.org/10.1094/PDIS-12-24-2663-RE.
DOI: https://doi.org/10.1094/PDIS-12-24-2663-RE

Interpretive Summary: Sugar beet roots in Idaho are held under ambient conditions in outdoor storage piles which can lead to fungal growth and rot and substantial loss of sugar. The fungal rots associated with roots held inside piles has been established in Idaho, but the incidence, distribution, and pathogenicity of fungi associated with fungal growth on the surface of sugar beet roots on top of outdoor piles has not been investigated. Therefore, the surface fungal growth on sugar beet roots held on top of 14 Idaho outdoor piles was assessed in 2018-19 and 2019-20. Cladosporium spp. were the only fungi covering more than 1% of the root surface (2 to 48%) on top of uncovered piles both years with the most frequently isolated species being C. cladosporioides, C. macrocarpon, and C. subtilissimum both years. The surface of roots after tarp removal on covered piles was also dominated by Cladosporium spp. (13 to 60%), but Penicillium spp. (0 to 35%), an Athelia-like basidiomycete (0 to 2%), and Botrytis cinerea (0 to 2%) were also frequently present. In pathogenicity tests, B. cinerea caused the most rot followed by Penicillium spp. The Cladosporium spp., Alternaria sp., and yeast (Candida and Holtermanniella spp.) led to little or no rot. Thus Cladosporium spp. seemed to largely be opportunistic spoilage fungi on the sugar beet root surface on top of outdoor piles, but workers should be cautious on or around these piles since some of the species are established to be associated with human clinical samples.

Technical Abstract: Sugar beet roots in Idaho are held under ambient conditions in outdoor storage piles which can lead to fungal growth and rot and substantial sucrose loss. The fungal rots associated with roots held inside piles has been established in Idaho, but the incidence, distribution, and pathogenicity of fungi associated with fungal growth on the surface of sugar beet roots on top of outdoor piles has not been investigated. Therefore, the surface fungal growth on sugar beet roots held on top of 14 Idaho outdoor piles [tarped ventilated (TV) piles and piles with no tarps or ventilation (NTV) at 7 locations] was assessed in 9 one-square meter areas per pile using a stratified random sampling design in 2018-19 and 2019-20. Pathogenicity was evaluated through sugar beet root plug inoculations conducted in commercial storage buildings. Cladosporium spp. were the only fungi covering more than 1% of the root surface (2 to 48%) on top of NTV piles both years with the most frequently isolated species being C. cladosporioides, C. macrocarpon, and C. subtilissimum both years. The surface of roots after tarp removal on TV piles was also dominated by Cladosporium spp. (13 to 60%), but Penicillium spp. (0 to 35%), an Athelia-like basidiomycete (0 to 2%), and Botrytis cinerea (0 to 2%) were also frequently present. Based on total fungal growth, NTV piles had 53 to 74% less (P < 0.0001) fungal growth than TV piles depending on year. Roots placed on the pile first (oldest roots) had more fungal growth than those in other pile areas based on Cladosporium spp., the Athelia-like fungus, and total fungal growth. In the plug assay, B. cinerea caused the most rot (P < 0.0001; averaged 31 to 32 mm of rot) followed by Penicillium spp. (P. expansum 14-22 mm, P. polonicum 14-16 mm, and P. cellarum 10 mm). The Cladosporium spp., Alternaria sp., and yeast (Candida and Holtermanniella spp.) led to little or no rot (0 to 2 mm). Thus Cladosporium spp. seemed to largely be opportunistic spoilage fungi on the sugar beet root surface on top of outdoor piles, but workers should be cautious on or around these piles since some of the species are established to be associated with human clinical samples.